1. Field of Invention
This invention relates generally to a water cooling system for an internal combustion engine, and more particularly to a cooling system and method for warming-up the engine at an early stage.
2. Description of Related Art
In an internal combustion engine for a vehicle, it is desirable to improve the performance of fuel consumption and to reduce an emission of an exhaust gas during early warm-up when starting the engine.
In conventional cooling systems for an internal combustion engine which include a heat accumulating container, a flow rate of the cooling water flowing to the internal combustion engine from the heat accumulating container is limited to the same flow rate that high-temperature cooling water, reserved in the heat accumulating container, flows into the heat accumulated container. Thus, warm-up of the internal combustion engine can only be performed by supplying the high-temperature cooling water reserved in the heat accumulating container at the same rate that it is being reserved therein. As a result, heating of the engine is inefficient because the heat provided to the internal combustion engine during warming-up operation is not efficiently accumulated in the engine.
It is an object of the present invention to solve the problems inherent in the prior art, such as e.g., by speeding up the warm-up process by increasing the flow rate of the high-temperature cooling water flowing through the internal combustion engine.
According to one aspect of the invention, a cooling system for an internal combustion engine, comprises: a cooling circuit that circulates cooling water through an internal combustion engine with a pump, a container including in reserve a quantity of a high-temperature cooling water heated by the internal combustion engine, and a controller that controls a flow rate of the cooling water within the internal combustion engine during warm up by supplying the internal combustion engine with the high-temperature cooling water reserved in the container at a flow rate greater than the flow rate of the cooling water into the internal combustion engine, and when introducing and reserving the high-temperature cooling water heated by the internal combustion engine into the container.
Another aspect of the invention according to the cooling system mentioned above includes a heating unit for heating the cooling water provided on a cooling water passageway through which the cooling water flows from the internal combustion engine to the container.
Another aspect of the invention according to the cooling system above includes cooling a drive motor that drives a water pump wherein the drive motor is controlled by a controller.
According to another aspect of the invention, a cooling method for an internal combustion engine comprises: varying the flow rate of the cooling water by setting the flow rate of the cooling water to high when the controller determines that the hot water heating control is to be performed; setting the flow rate of cooling water to low when the controller determines that the heat accumulating control is to be performed; setting the flow rate of cooling water to intermediate when the controller determines that the heating mode is to be performed.
A further aspect of the invention, according to the cooling method of an internal combustion engine comprises: varying the flow rate of cooling water with a pump driven by a drive motor that is controlled by a controller. A rotation rate of the drive motor is set to a high level and the flow rate produced by the water pump is high when the controller determines that the hot water heating control is to be performed. A rotation rate of said drive motor is set to a low level and the flow rate produced by the water pump is low when the controller determines that the heat accumulating control is to be performed. And, a rotation rate of said drive motor is set to an intermediate level and the flow rate produced by the water pump is intermediate when the controller determines that the heating mode is to be performed.
In this cooling system, when the internal combustion engine is warmed up by supplying it with the high-temperature cooling water reserved in the container, the controller increases a flow rate of the cooling water within the internal combustion engine. When the flow rate of the cooling water in the internal combustion engine increases, a heat transfer coefficient between a wall surface of the internal combustion engine and the cooling water rises. Hence, the heat from the cooling water is easily transferred to the internal combustion engine, such that the internal combustion engine can be quickly heated.
Alternatively, when introducing and reserving high-temperature cooling water in the container, the high-temperature cooling water heated by the internal combustion engine and the flow rate of the cooling water in the internal combustion engine becomes lower than in the warm-up operation. When the flow rate of the cooling water is low, the heat transfer coefficient between the wall surface of the internal combustion engine and the cooling water decreases. Therefore, a high temperature of the internal combustion engine can be produced. Further, when the flow rate of the cooling water in the internal combustion engine is low, a heat receiving time for which the cooling water receives the heat from the internal combustion engine is elongated. As a result, the temperature of the cooling water effluent from the internal combustion engine can be increased, such that the higher-temperature cooling water can be reserved in the container.
According to the invention, the controller can variably control a discharge quantity of a variable capacity pump provided in a closed circuit that connects the internal combustion engine to the container. Alternatively, the controller can control a valve provided in the closed circuit that connects the internal combustion engine to the container.
According to an exemplary embodiment the internal combustion engine is warmed up by supplying the internal combustion engine with the high-temperature cooling water reserved in the container before starting the internal combustion engine. This is because the internal combustion engine is heated before starting, and combustion of the internal combustion engine at a start of the internal combustion engine can therefore be set to a preferred state. Accordingly, a fuel consumption and an emission of exhaust gas can be improved.
According to the invention, a heating unit for heating the cooling water can be provided in a cooling water route through which the cooling water flows to the container from the internal combustion engine. In addition to heating by the exhaust heat from the internal combustion engine, the heating unit can provide heat to the cooling water. The cooling water is then introduced into the container whereby the higher-temperature cooling water can be put into the container. The heating unit can be, for example, a combustion heater that burns a fuel in a combustion chamber, different from the internal combustion engine for heating the cooling water, an electric heater, and so on.